Method of forming gelatin image

ABSTRACT

A METHOD OF PREPARING A GELATIN IMAGE, WHICH COMPRISES FORMING AN ELECTROSTIC LATENT IMAGE ON AN ELECTROPHOTOGRAPHIC LIGHT-SENSITIVE LAYER; CONVERTING SAID LATENT IMAGE INTO A GELATIN IMAGE USING AN ELECTROPHOTOGRAPHIC DEVELOPER CONTAINING GELTAIN FINE GRAINS; APPLYING SMALL DROPLETS OF WATER TO THE SURFACE OF SAID LIGHT-SENSITVE LAYER CARRYING SAID GELATIN IMAGE; SAID WATER BEING IN AN AMOUNT SUFFICIENT OT ADHERE THE GELATIN FINE GRAINS FORMING SAID GELATIN IMAGE TO THE SURFACE OF SAID LIGHT-SENSITIVE LAYER; AND, HARDENING SAID GELATIN IMAGE, IS DISCLOSED.

United States Patent 3,677,766 METHOD OF FORMING GELATIN IMAGE Yasui Tamai, Sadao Osawa, and Seiichi Taguclu, Saitama, Japan, assignors to Fuji Photo Film Co., Ltd., Minami-Ashigara-machi, Kanagawa, Japan No Drawing. Filed Feb. 20, 1970, Ser. No. 13,238 Claims priority, applizatliggilgapan, Feb. 21, 1969,

Int. Cl. G03g 13/10, 13/20, 13/22 US. Cl. 96-1 LY 6 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a method of forming a gelatin image and more particularly, it is concerned with a method of forming a gelatin image by developing an electrostatic latent image obtained by an electrophotographic method to convert it into a gelatin image.

(2) Prior art It is well known that the utilization of a gelatin image serves to obtain a color print of good quality. This is the so-called dye transfer process wherein the tanning development is carried out by the use of a silver halide emulsion and the thus resulting gelatin relief is utilized. The dye transfer process can give an image of high durability and good quality. Since the technique employed in the dye transfer process is similar to that of printing, it is profitable to make a number of reproductions from the same original but not to make a small number of reproductions. In the latter case, the cost per sheet of reproductions is considerably high. The reason is that formation of a gelatin relief image takes time and skill.

A method has been disclosed utilizing an electrophotographic process as a simple method for making a gelatin matrix (Belgian Patent No. 724,581). For example, this method of making a gelatin image comprises the steps of (I) Charging uniformly a light-sensitive layer for electro photography in the dark and then subjecting the lightsensitive layers to form an electrostatic latent image;

(11) Developing the light-sensitive layer carrying the electrostatic latent image by the use of an electrophotographic developer containing a gelatin toner; and

(III) Hardening with the purpose of fixing the resulting gelatin image.

The sheet possessing the thus obtained gelatin image can be used as a gelatin relief for dye transfer. That is to say, a dye image can be obtained by the following three steps,

(IV) Contacting the gelatin image with an aqueous solution of a water-soluble dye to absorb the dye in the image; and

(V) Arranging another sheet having a surface layer capable of absorbing readily the dye in such a manner that the layer to be dyed is brought into contact with the gelatin image, whereby the dye is transferred to the layer to form finally a color image on the sheet and repeating steps (IV) and (V) using the same gelatin relief to obtain a number of sheets having the dye image.

It was found, however, as a result of studies on the above-mentioned method that the repeated use of the gelatin relief results in problems, that is, unevenness in image density and many scratches on image. These disadvantages are due to the fact that the gelatin image obtained in the step (II) is weak mechanically. That is to say, the adhesion of gelatin toner to a light-sensitive layer and that of gelatin toners to each other are not so good.

As the electrophotographic developer containing the gelatin toner in the foregoing step (H), such a liquid developer is often used with the gelatin toner being contained in a carrier liquid having a resistance of 10 9 cm. or more. In many cases, a resin varnish soluble in the carrier liquid is incorporated in this liquid developer. It may be considered that the fixing of a gelatin image, in general meaning, is favorably carried out by the action of such a resin varnish and the subsequent hardening treatment of gelatin.

The problem of concern now may be considered to be due to an insufficiently durable image once fixed. As a method for solving this problem, gelatin toner may be fixed by providing a thin layer of fixing resin on a sheet surface after forming a gelatin image. This method has, however, the disadvantage that the transfer of a dye in the steps of (IV) and (V) tends to be hindered to give finally a low image density.

It is an object of the invention to provide an improved method for making a gelatin relief image by electrophotographic process.

It is another object of this invention to provide a treatment method for increasing the durability of a gelatin image obtained by developing an electrostatic latent image with an electrophotographic developer containing gelatin fine powder.

It is a further object of the invention to provide a method of making a gelatin image, excellent in durability,

used for obtaining a color print by the dye transfer process.

DESCRIPTION OF THE INVENTION The foregoing objects of this invention can be accomplished by the discovery of a method of making a gelatin image. The method comprises forming an electrostatic latent image on a light-sensitive layer for electrophotog raphy; converting said latent image into a gelatin image by the use of an electrophotographic developer containing gelatin fine grains; feeding to the surface of said lightsensitive layer carrying said gelatin image water in an amount suificient to adhere the gelatin fine grains forming said gelatin image to the surface of said light-sensitive layer in the form of fine droplets, e.g., steam or aerosol spray and then hardening said gelatin image. That is to say, applying water in the form of steam or an aerosol to the sheet surface after development but prior to the hardening treatment of the gelatin image results in a finally hardened gelatin image having excellent durability. In some cases, the sheet may be heated at 35 C. or more during the same time. When the Water is fed under this warmed state, the toners in the gelatin image adhere immediately to each other and a very high durability is given by the next hardening treatment. The gelatin toner swells with water to give a tackiness and strong bond between the toner and light-sensitive layer surface.

In the field of conventional electrophotography, there is a technique, a solvent vapor fixing method, wherein a vapor of an organic solvent is applied to a binder contained in a conventional toner thereby fixing the toner image. In the present invention, however, a special toner for electrophotography, that is, a gelatin toner, is used.

Consequently, fixing with an organic solvent is impossible and water must be used. It was found that a complete gelatin image is obtained by eifecting the step of hardening the gelatin after fixing the gelatin toner with water and drying sheet. It was further found that, when a sheet is immersed in an aqueous solution containing a hardener directly after development without applying water in the form of fine droplets such as steam or an aerosol, to the surface therof, there is formed a defect of flow form in the gelatin image.

It may be considered to immerse a sheet of water after hardening the gelatin image but this is undesirable for obtaining a gelatin image excellent in durability. Preferably the surface is exposed to steam directly after developing and drying whereby a highly fixed image is obtained without scratching. In this case, the immersion of a sheet in warm water for applying water thereto is unsatisfactory since the gelatin toner forming an image is dissolved. Therefore, it is preferred to feed water in the form of droplets of steam or vapor. During the application, the surface of the sheet is preferably held at a temperature of 30 C. or higher, since gelatin toner has a suitable tackiness at this temperature. It may also be considered to melt a gelatin layer during hardening but the toner contained therein becomes hard to resist cold water possibly due to its fine grain size. It is desirable in practice, therefore, to effect the step of applying steam prior to hardening.

Application of steam can be carried out at a temperature of lower than 100 C. (1 atm.) but large drops of more than 0.1 mm. in diameter must be avoided from the steam, since large water drops in adhesion to a sheet surface deteriorates the image.

Feeding of water to the sheet can be carried out by placing the sheet in an atmosphere at a high temperature and high humidity. For example, the developed sheet is arranged for 5 minutes in a closed vessel at a temperature of 40 C. and a relative humidity of 90% to thus fix a toner image. Furthermore, feeding of water to a sheet can be carried out by the use of a spray adjusted so that no large water droplets are formed. Water is sprayed over the entire surface of the sheet followed by drying by warm air, thereby fixing the toner image. In case the diameter of water drop exceeds 0.1 mm., visible scratches appear in an image.

In feeding the water to the sheet surface, too little yields incomplete fixing while too much yields a layer of water movable on the sheet surface and results in flow type problems in an image. Sufficient water is applied when the gelatin toner adheres to the light-sensitive layer. Moreover, feeding of water in the form of small droplets results in easy control of the steam or aerosol, the amount thereof which is fed and also prevents scratching of the image.

Judgment as to whether the firing is carried out completely or not is practiced by drying adequately a sheet surface sprayed with water and then rubbing an image area by finger. If the fixing is completed, the gelatin toner is no longer strippable from the surface of the light-sensitive layer.

Gelatin toner is thereby fixed with steam. The thus obtained sheet is immersed in a bath containing a hardener, warmed and dried, whereby to harden the gelatin toner, forming an image. As such hardeners are gelatin hardeners for conventional photography, preferably, an alcohol-soluble or acetone-soluble hardener, with good results. For example, a solution consisting of 90 parts of methyl alcohol, 9 parts of water and 1 part of formaldehyde is execellent for simplicity of processing. A gelatin image is hardened, for example, by immersing a sheet carrying the gelatin image in this solution for from 10 to 30 seconds and then allowing the sheets to stand at room temperature for about 5 hours.

An electrophotographic light-sensitive layer used in this invention contains generally a photoconductive compound and an insulating resin. In particular, it is desirable to use photoconductive zinc oxide as the photoconductor. A support of the light-sensitive layer has preferably a high durability. Furthermore, a low electric resistance layer is ordinarily provided between the light-sensitive layer and the support.

An electrophotographic developer containing gelatin fine grains, used in the invention, is preferably a liquid developer consisting of a nonpolar organic solvent having a high electric resistance (generally more than 10 2 cm.) which will hereinafter be referred to as the carrier liquid and gelatin fine grains contained therein.

Where the electrophotographic light-sensitive layer of the invention contains a photoconductive zinc oxide, a treatment for removing zinc oxide using an acid can be carried out after the foregoing hardening treatment of a gelatin image. This is a treatment such that an acid dye is absorbed in a gelatin image well in the case of using the gelatin image for the dye transfer process.

Thus, a gelatin relief having mechanically suflicient strength is obtained. This gelatin image is adapted to the dye transfer process to obtain a color image as follows. The gelatin image is contacted with an aqueous solution of an acid dye or a mordant dye and the dye as absorbed in the gelatin image area. The foregoing step (V) is then carried out to obtain a color image.

An image obtained according to the invention has a very high quality, high light resistance and excellent color quality. According to the method of this invention, a deep color con be reproduced due to the absence of surface refiection, as compared with the image obtained using electrophotographically various pigment toners. In the case of composing a multi-color image, each color is so transparent that the color mixing is complete and true color reproduction is possible.

Furthermore, a gelatin image once obtained can repeatedly give a color image through dye transfer by supplying a dye and a number of prints can therefore be made economically.

The following examples are to illustrate the invention in detail without limiting it. All parts are parts by weight.

EXAMPLE 1 To a 5 g. of gelatin, photographic grade, g. of distilled water was added, the gelatin swelling after 30 minutes. The mixture was then warmed at 60 C. to obtain a transparent aqueous gelatin solution.

To 10 ml. of the aqueous gelatin solution held at 45 C. were added methanol until a slight white turbidity appeared, amounting to 11 ml., and then 0.5 ml. of distilled water to diminish the white turbidity. A solution of the gelatin in a mixed solvent of water and methanol was thus obtained and the entire amount was dispersed in the following liquid by ultrasonic stirring:

Acetone 980 Cottonseed oil 20 to obtain a milk-white dispersion of gelatin. To the dispersion was added, with agitation, the following solution. Ml.

Varnish obtained by cooking a resin-modified phenolformaldehyde resin and linseed oil 4 Toluene 36 tin fine grains. The entire amount of the precipitate was added to the following mixed solvent and stirred.

Ml. Toluene 20 Xylene 3.5 Cottonseed oil 6 Ml. Cyclohexane 1,600 Kerosene 400 A light milk-white liquid for electrophotography was thus obtained. The kerosene was added for the purpose of lowering the evaporation speed of the liquid developer. The gelatin toner in the liquid developer had a positive charge.

On the other hand, 100 parts by weight of a photoconductive zinc oxide and 20 parts of an epoxyester of dehydrated caster oil fatty acid were mixed with a suitable amount of toluene to give a uniform coating liquid. To the liquid were added 0.02 part of fluorescein and 0.2 part of tetrabromophenol blue dissolved in a small amount of ethylene glycol monomethyl ether to expand the light sensitivity of the zinc oxide to the entire range of visible range. Further, a suitable amount of toluene was added thereto and coated onto an aluminum deposited polyethylene terephthalate film of 90 microns in thickness to give a dried thickness of about 8 microns. The thus obtained film, dried adequately in the dark, performed well as an electrophotographic sensitive material.

The resulting electrophotographic sensitive material was exposed to negative corona discharge in the dark to charge electrostatically the surface uniformly and then placed in an enlarger where it was subjected to projection exposure using a color slide as an original on which a red filter was superposed.

The exposed sensitive material was wetted with pure kerosene and immediately immersed in the foregoing liquid developer. Using a stainless steel tray during the same time, the latent image surface was allowed to be near the bottom of the tray which played the role of the developing electrode. The sensitive material was withdrawn after immersion for about 90 seconds, rinsed with isoparafiinic solvent and dried.

The sheet surface carrying the gelatin toner image was then held over a beaker in which 1000 ml. of water was boiling vigorously for an interval of 30 cm. After 10 seconds, it was observed, the gelatin toner image, looking initially whitish, became uniformly transparent. When the sheet was adequately dried again and the gelatin toner area was rubbed with a finger, the gelatin toner was adhered strongly to the surface of the light-sensitive layer.

Then, the fixed sheet was immersed in a methanol bath containing 1% formaldehyde, allowed to stand at room temperature for 2 hours thereby hardening the gelatin image.

The sheet was immersed in a 50% acetic acid bath to remove the zinc oxide contained in the light-sensitive layer. Zinc oxide was removed from the surface of the lightsensitive layer and the entire surface possessed a metallic lustrous appearance due to the aluminum layer under the light-sensitive layer.

The sheet was further washed adequately with distilled water, finally immersed in methanol, withdrawn and dried with warm air.

A gelatin relief for cyan print was obtained by the foregoing operations.

Similarly, another sheet was subjected to exposure using the same original and a green filter in combination and to the above-described developing treatment to obtain a relief for magenta print. Combining with a blue filter similarly, a relief for a yellow print was obtained. The three reliefs were respectively immersed in aqueous solutions of Acid Blue 54 (Antraquinoric dyestuff), Acid Violet 7 (Cl. 18055) and Acid Yellow 23 (CI. 19140) for 2 minutes, withdrawn and washed with a dilute acetic aqueous solution.

On the other hand, a gelatin layer-possessing sheet to be dyed was immersed in aluminum sulfate solution, positioned on the three reliefs in turn of register and pressed thereto. The dye absorbed in each toner image was transferred to the gelatin layer by this step thus to obtain very high quality reproduction. The relief was resistant to use of about runs.

COMPARATIVE EXAMPLE The same procedures as described in Example 1 were repeated but without fixing by steam to obtain a gelatin relief and, after the dye absorption, an image was obtained by transferring. In the image were found a partial lowering of the optical density and fine scratches. These problems were possibly due to the fact that the fixing was insufiicient and the gelatin toner image area was damaged during processings.

EXAMPLE 2 In place of fixing by steam in Example 1, fixing was carried out in a casing at high temperature and high humidity.

Water was charged in the bottom of a metal casing of 50 cm. x 40 cm. x 10 cm., the entire casing being placed in an air thermostat at 45 C. A sheet after development was placed in the upper part of the casing, withdrawn after 3 minutes and dried adequately. The gelatin toner was completely fixed. The gelatin was then hardened by the same procedure as that of Example 1, whereby a strong gelatin image was obtained.

EXAMPLE 3 Percent by volume Formaldehyde Water 4 Methanol 47 Acetone 47 When it was then taken out of the solution and allowed to stand at 25 C. for 5 hours, the gelatin image adhered and hardened completely.

What is claimed is:

1. A method of preparing a gelatin image which comprises forming an electrostatic latent image on an electrophotograp hic light-sensitive layer; converting said latent image into a gelatin image using a liquid electrophotographic developer containing gelatin fine grains drying to remove said liquid electrophotographic developer; applying small droplets of water of a diameter not exceeding 0.1 mm. to the surface of said light-sensitive layer carrying said gelatin image, said water being in an amount sufficient to adhere the gelatin fine grains forming said gelatin image to the surface of said light-sensitive layer; and hardening said gelatin image.

2. The method of preparing a gelatin image as claimed in claim 1, wherein said surface of said light-sensitive layer carrying said gelatin image is heated at a temperature of more than 35 C., during the application of water.

3. The method of preparing a gelatin image as claimed in claim 1, wherein the droplets of water are steam.

4. The method of preparing a gelatin image as claimed in claim 1, wherein the droplets of water are obtained from an aerosol.

5. The method of preparing a gelatin image as claimed in claim 1, wherein said small droplets of water are applied by contacting said surface of said light-sensitive layer carrying said gelatin image with an atmosphere containing high humidity.

6. The method of preparing a gelatin image as claimed in claim 1, wherein said small droplets of water are water vapor.

References Cited GEORGE F. LESMES, Primary Examiner 10 R. E. MARTIN, Assistant Examiner US. Cl. X.R. 

